Many areas for playing sports or engaging in recreational activities, such as ice hockey rinks, roller skating (including in-line hockey) rinks, indoor soccer fields, indoor football fields, short track (or other) speed skating rinks, and indoor handball fields, have an exterior perimeter defined by wall panels. These wall panels are often referred to as “dasher boards,” particularly in ice and in-line hockey and short track speed skating rinks. If a participant within such an area contacts the dasher boards at high speed, with high energy, and/or in an awkward position, serious injuries can result including concussions and neck and spinal cord injuries.
A number of prior art patented and commercial proposals and systems have sought to reduce the number or extent of injuries as a result of high speed, high energy, and/or awkward human contact with dasher boards. For example as early as 1983 Swiss Patent 645,275 considered hockey player safety as one motivation in providing a rubber plate at the bottom of a mounting system for dasher boards. In 1988 the disclosure in U.S. Pat. Nos. 4,888,367 and 4,927,134 dealt primarily with hockey player safety in employing a mounting system at the base of dasher boards that allowed the boards to pivot against the adjustable bias of spring elements to absorb the force of high energy impacts of players against the boards. In the late 1990s as a precursor to the ATHLETICA commercial ice hockey rink dasher board assemblies U.S. Pat. No. 6,004,217 proposed a number of alternative systems for absorbing impact forces such as pivoting a dasher board with respect to a lower frame against spring pressure, or providing discrete widely spaced compressible coil springs between a dasher board and vertical frame elements spaced along the height of the dasher board. In 2007 the inventors of U.S. Pat. No. 7,914,385 proposed utilizing a viscoelastic acrylic foam tape for attaching a dasher board to vertical posts and horizontal stringers of a dasher board frame to provide some energy absorption. Research related to dasher board safety systems continues today, as shown by Canadian patent application 2,708,199 published Jan. 5, 2012.
While some of the above proposals and systems can significantly reduce the probability of injury to players or participants impacting dasher boards at medium or high portions of the dasher boards, impacts at lower portions of the dasher boards are much more problematic. Also many prior art systems cannot achieve the desired level of protection to prevent or minimize the severity of concussions when the impacts are at high speed and/or energy, concussions almost universally occurring if the Head Injury Criteria (HIC-14) is 250 or more. HIC is determined by the following formula:
      H    ⁢                  ⁢    I    ⁢                  ⁢    C    =            {                                    (                                          t                2                            -                              t                1                                      )                    ⁡                      [                                          1                                                      t                    2                                    -                                      t                    1                                                              ⁢                                                ∫                                      t                    1                                                        t                    2                                                  ⁢                                                      a                    ⁡                                          (                      t                      )                                                        ⁢                  dt                                                      ]                          2.5            }        ⁢    max  
According to the present invention a dasher board assembly is provided having enhanced safety, especially for impacts at lower portions of the dasher board. The assembly according to the present invention reduces HIC (compared to a rigid dasher board frame assembly) by at least 30%, and typically by more than about 60%, at virtually all practical impact speeds and energy levels at substantially any portion of a dasher board. For example according to the assembly of the invention at a test (not with a human participant) speed of over 18 mph HIC was reduced by about 68% compared to a rigid dasher board frame system. In any case, according to the invention for virtually every realistic scenario HIC is less than 250, often less than 50.
According to one aspect of the present invention a dasher board assembly providing enhanced safety comprises a frame and a substantially rigid (e.g. HDPE, or the other exemplary materials mentioned in U.S. Pat. No. 7,914,385, or mandated by any regulatory body) dasher board operatively attached to the frame and having a top area and bottom area. The frame is constructed, and the dasher board is operatively attached to the frame, so that when the top area of the board is impacted the assembly will absorb the force of impact primarily in a first mode of absorption, and so that when the bottom area of the board is impacted the assembly will absorb the force of impact primarily in a second mode of absorption.
Desirably the first mode of absorption comprises deflection of the frame, and the second mode of absorption comprises compression of a dampening material. Also when the top area of the board is impacted the assembly will also absorb the force of impact in the second mode of absorption in addition to the first mode.
In a preferred manner this is accomplished in part by providing a dampening material of particular characteristics between the dasher board and frame. Particular parameters for evaluating effective operation of dampening material according to the invention are often not readily available. While “damping coefficient” and “spring constant” are good parameters for objectively determining the ability of some devices or materials to dissipate energy, they do not completely directly translate to other materials. For some materials, such as foam (like rebond or type 1850 foam), loss coefficient is a desirable parameter. Loss-coefficient (typically indicated by the Greek letter η) measures the degree to which a material dissipates vibrational energy.
Given the limitations of one or more parameters being definitive in quantitatively defining the ability of the dampening material according to the invention to effect proper damping so as to assure that HIC is always below 250, it is to be understood that the parameters set forth will not be exactly precise for all materials. However, even if they are not precisely correct they provide definitive enough information for one or ordinary skill in the art to properly select the particular features of a given material to be employed.
The dampening material desirably utilized according to the invention will be substantially continuous and have a damping coefficient of about 1.7-3.2×104 Newton seconds per meter and/or a spring constant of about 1.5-3.0×106 Newtons per meter. Where the dampening material is foam it desirably has a loss coefficient η of more than 0.15.
The frame preferably comprises cantilevered vertical frame elements (e.g. rectangular aluminum tubes), and the first mode of absorption preferably comprises deflection of the cantilevered vertical frame elements.
As earlier indicated, the first and second modes operate so that an HIC value of less than 250, preferably even 50 or less, results from the impact of a human being against the dasher boards during all practical scenarios.
According to another aspect of the present invention there is provided a dasher board assembly comprising: A frame including a plurality of substantially vertical frame elements and a plurality of substantially horizontal frame elements; at least one substantially rigid dasher board operatively connected to the vertical and horizontal frame elements; a dampening material operatively provided between the dasher board and the frame elements, the dampening material having a plurality of openings therein; a plurality of fasteners operatively connected to the board substantially in alignment with the openings, and passing therethrough; and a plurality of openings in the frame elements substantially in alignment with the dampening material openings, the fasteners passing therethrough so as to be movable with respect to the frame elements.
The dasher board has upper and lower areas; and desirably the substantially vertical frame elements are mounted and constructed (e.g. cantilevered aluminum elements, such as AL 6061 T6 rectangular hollow tube extrusions) so that they flex when the upper area is impacted by a human being. Desirably the assembly defines a sporting or recreational area selected from the group consisting essentially of ice and in-line hockey rinks, roller skating rinks, indoor soccer fields, indoor football fields, speed skating rinks, and indoor handball fields.
According to another aspect of the present invention there is provided a dasher board assembly comprising: A frame including a plurality of substantially vertical frame elements and a plurality of substantially horizontal frame elements; at least one substantially rigid dasher board operatively connected to the vertical and horizontal frame elements; and a dampening material operatively provided between the dasher board and at least most of the frame elements, the dampening material having a damping coefficient of about 1.7-3.2×104 N-s/m, and a spring constant of about 1.5-3.0×106 N/m. For example the dampening material may have a damping coefficient of about 2.7×104 N-s/m, and a spring constant of about 2.4×106 N/m, or both may have a value of about 2.
The dampening material may be foam with a η value of 0.15 or more. One particular foam that may be utilized is rebond foam about 2.5-4 inches thick. Seven pound per cubic foot density rebond foam is particularly desirable, such as is used conventionally in 1.5 or 2 inch thickness for gymnasium wall padding. Alternatively foam type 1850 about 2.5-4 inches thick may be utilized. In any case the thickness must be such that the foam will not “bottom out” when it is compressed by the maximum practical impact force, but any thickness more than that is wasted.
The thickness of the foam may vary over the height of the frame, for example having a different thickness near the bottom than near the top, or the same thickness with a different damping coefficient and/or spring constant and/or η value near the bottom.
According to yet another aspect of the present invention there is provided a dasher board assembly which comprises the following elements: A frame including a plurality of substantially vertical frame elements having top and bottom areas, and a plurality of substantially horizontal frame elements. At least one substantially rigid dasher board operatively connected to the substantially vertical and horizontal frame elements. The substantially vertical frame elements comprise cantilevers constructed and positioned so that upon an impact force at the top area at least one of the vertical frame elements will deflect a maximum of about two-four inches to dampen the force of the impact. The substantially vertical frame elements preferably comprise cantilevered aluminum tubes that are polygonal in cross-section, such as AL 6061 T6 rectangular hollow tube extrusions.
The dasher board assembly according to the invention has an HIC-14 value at least 30% less, desirably about 60% less, than a comparable assembly wherein the frame is rigid (e.g. wood, rigid metal, or a combination thereof). In any case the HIC value will be less than 250 for all practical scenarios.
It is the primary object of the present invention to provide a dasher board system with enhanced safety for participants within an area encompassed by the dasher boards. This and other objects of the invention will become clear from the detailed description of the invention, and from the appended claims.